1. Field of the Invention (Technical Field)
The invention relates to sheet metal duct forming equipment and more particularly to sheet metal duct notching templates.
2. Description of the Related Art Including Information Disclosed under 37 C.F.R. .sctn..sctn.1.97-1.99 (Background Art)
In manufacturing sheet metal ducts, they are made in one, two, three and four pieces, for example a complementary pair of "half wrap" ducts are cut and formed, and then fastened together. For each half wrap, a substantially rectangular piece of sheet metal, precut to size and called a "block-out," is marked, usually by scribing, for notching and folding. The scribing process is conventionally done manually in most sheet metal shops. At the present time the existing tool generally used is known as a circumference rule: simply a long metal ruler, containing measuring indicia and marked in inches in the United States. The circumference rule is used with an adjustable scribe, which is a separate tool. Too, some practitioners use L-squares, T-squares, tri-squares, combination squares, or other such devices in order to get notch consistency. Practitioners also use various types of notches, some of which are not compatible with others if placed to fit together. Some types of notches are used in order to save time. Other notch types are used to do a top quality job.
U.S. Pat. No. 2,632,250 to Rauser discloses a sheet metal layout device for inscribing sheet metal.
U.S. Pat. No. 1,636,025 to Waelde describes a sheet metal layout tool which utilizes diagonally disposed aperture arrays or matrices.
U.S. Pat. No. 2,332,568 to Gauthier discloses a tool for laying out sheet metal, having collars or bushings slidably mounted on a graduated bar for indicating the measurements of the pieces to be cut.
U.S. Pat. No. 4,519,143 to Correlli discloses a marker system for use in marking lines on sheet metal which is to be subsequently bent. Provision is made for marking from the left- or the right-hand margin.
U.S. Pat. No. 4,507,869 to Stude discloses a marker attachment for slidable mounting on an elongated rule and having provision for guiding a pencil or other marking device.
While these devices offer some desirable features, an apparatus in accordance with the instant invention offers ease of use, increased speed, certain accuracy, and is inexpensive to construct.